Floating roofs on liquid storage tanks, particularly those storing petroleum chemical liquids, are well known. It is also well known that petroleum tanks emit vapors and odors that are not pleasant to inhale, and are increasingly violations of emissions laws and subject to governmental controls. For example, see 40 C.F.R. 60 for the U.S. Environmental Protection Agency regulations, as well as other state and local laws. Such vapors and odors are the result of inadequate vapor sealing to prevent the petroleum vapors in the storage tank from escaping to the surrounding atmosphere. Floating roofs contain the vapors from the liquid immediately under the roof, but wherever the roof does not cover the liquid, vapors are able to escape. The large area of this type is that ring between the outer edges of the roof and the wall of the tank. Single or double rings of flexible sheet material, such as rubber, are used to prevent the vapors from escaping around the edges of the roof while permitting limited lateral movement of the roof, as well as vertical movement. Another potential leak for vapors is around the gauge well pipe that is used to take samples from the stored liquid at various depths for analysis. A typical sample taking system is described in my U.S. Pat. No. 5,138,891, which is incorporated herein for reference. The present invention is an improvement upon the invention of that patent in that it provides a vapor seal system to be used to substantially prevent vapors from leaking past the gauge well pipe and beyond the roof to the atmosphere.
It is an object of the invention to provide a vapor seal for use between the gauge well pipe and the gauge well sleeve in a liquid storage tank having a floating roof that accommodates for vertical and lateral movement of such roof while an effective vapor seal is maintained. It is another object of this invention to provide such a seal of vapor-impervious flexible sheet material fastened at the upper end to the floating roof and at the lower end to a weighted shoe sliding vertically on the gauge well pipe. Still other objects will become apparent from the more detailed description which follows.